The invention relates to a wheel hub-constant velocity joint unit in which a wheel hub with a passage opening that carries inner shaft teeth is held under tension with the outer joint part of a constant velocity joint on which a journal with outer shaft teeth is formed, wherein inner shaft teeth of the passage opening and outer shaft teeth of the journal mesh with each other and a double-row wheel bearing is pushed onto the wheel hub that comprises an inner bearing ring on which a front face of the outer joint part is directly supported. A screw that is supported on the outside on the wheel hub and that is screwed into a threaded hole in the journal is used for the tensioning. Arrangements of this type are used on drive wheels, in particular, the wheels used for steering motor vehicles, wherein the wheel and also, if necessary, a brake disk are screwed onto the flange of the wheel hub, while the constant velocity joint forms an integral component of a drive shaft (side shaft) that is made from an intermediate shaft, an inner sliding joint, and the constant velocity joint named here that can be constructed as a constant velocity joint (front-wheel drive) or also as a sliding joint (rear-wheel drive). The bearing arrangement is to be used in a wheel carrier or steering stub axle.
In known arrangements of the noted type, the design is directed toward dimensioning the wheel bearing as small as possible, both for reasons of cost with respect to the wheel bearing and also in terms of the overall size of the wheel carrier or steering stub axle. Under the mentioned point of view, the journal diameter on the outer joint part is designed for the minimum required strength, wherein the journal diameter simultaneously defines the inner diameter of the wheel hub and thus indirectly, via the strength-dependent wall thickness of the hub, the inner diameter of the wheel bearing. Due to the elasticity of the journal designed in this way, a change in torque, in particular, an abrupt change in torque guided through the arrangement leads to relative movements between the outer joint part and the inner ring of the wheel bearing on the mutual stop surfaces. This leads to noise being generated and also to sliding fit corrosion of the fitting and to the loss of the clamping force of the connection.
Starting from these conditions, the invention is based on the objective of providing a novel concept for a unit of the mentioned type that guarantees a higher bearing and connecting strength for a shorter construction and avoids the disadvantages named above.
This is achieved according to the invention by a wheel hub-constant velocity joint unit in which a wheel hub with a passage opening that carries inner shaft teeth is tensioned with the outer joint part of a constant velocity joint, wherein a journal with outer shaft teeth is formed on the constant velocity joint. Here, the inner shaft teeth of the passage opening and the outer shaft teeth of the journal engage one in the other and a double-row wheel bearing is pushed onto the wheel hub. The wheel hub comprises an inner bearing ring on which an end face of the outer joint part is directly supported. According to the invention, a pitch circle diameter of the roller bearing is greater than a pitch circle diameter of the constant velocity joint. In other words, a ratio of the pitch circle diameter of the roller bearing to the pitch circle diameter of the constant velocity joint is greater than 1.
Preferred embodiments and improvements are listed below.
The ratio of the pitch circle diameter of the roller bearing to the pitch circle diameter of the constant velocity joint is especially preferred from a range between 1, and 1.6, i.e., greater than 1, and less than 1.6.
Advantageously, the distance between the joint shaft center and the contact point of the wheel bearing is less than half the sum from the pitch circle diameter of the roller bearing and the ball diameter of the balls of the constant velocity joint (or the joint balls, also “ball joint”).
Therefore, in this embodiment the distance of the joint and bearing in ratio to the appropriate pitch circle diameters is reduced in size. In this way, an increase in the tilting strength of the bearing and an increase in the bearing capacity and thus the bearing service life can be achieved.
In another preferred embodiment, a journal shaft of the joint shaft is less than the distance between the joint shaft center and the contact point of the wheel bearing or the ratio of the journal length of the joint shaft to the distance between the joint shaft center and the contact point or the contact plane of the wheel bearing is less than 1, i.e., LZ/B<1.
In another preferred embodiment, the ratio between the bearing width and the distance between the joint center and the contact point is greater than 1, i.e., BL/B>1.